The present invention relates to a process for production of arachidonic acid. The present invention also relates to a food product and a method to make the food product containing such arachidonic acid.
Arachidonic acid (all-cis-5,8,11,14-eicosatetraenoic acid) is a polyunsaturated fatty acid (PUFA) containing 20 carbon atoms with four double bonds. The double bonds are arranged with the last one located six carbon atoms from the methyl end of the chain. Therefore, arachidonic acid is referred to as an omega-6 fatty acid. Arachidonic acid is one of the most abundant C20 PUFA""s in the human body. It is particularly prevalent in organ, muscle and blood tissues. Arachidonic acid is a direct precursor for a number of circulating eicosenoids, such as prostaglandins, thromboxanes, leukotrienes and prostacyclins, which are important biological regulators. These eicosenoids exhibit regulatory effects on lipoprotein metabolism, blood rheology, vascular tone, leukocyte function, platelet activation and cell growth. The application of arachidonic acid to an infant""s diet is particularly important due to the rapid body growth of an infant. Arachidonic acid is an important precursor to many of the eicosanoids which regulate cellular metabolism and growth in infants. It is found naturally in human breast milk but not in most infant formula. In an effort to have infant formula match the long chain fatty acid profile found in breast milk, scientific and food regulatory bodies have recommended that arachidonic acid be added to infant formula, especially in formula utilized for premature infants.
In particular, it is preferable that arachidonic acid containing oil produced for use with infant formula contain little or no other long chain highly unsaturated fatty acids (e.g., eicosapentanoic acid). Such other long chain highly unsaturated fatty acids are not preferred because some of these fatty acids can interfere with the utilization of arachidonic acid by the infant, and/or can inhibit blending of the arachidonic acid-containing oil with other oils to achieve the appropriate ratio of fatty acids matching breast milk or other desired applications. Highly unsaturated fatty acids are defined as fatty acids containing 4 or more double bonds.
Traditional sources of arachidonic acid include poultry eggs, bovine brain tissue, pig adrenal gland, pig liver and sardines. The yield of arachidonic acid, however, is usually less than 0.2% on a dry weight basis. The use of microorganisms capable of producing arachidonic acid de novo have been suggested by various investigators, including Kyle, PCT Publication No. WO 92/13086, published Aug. 6, 1992; Shinmen et al., U.S. Pat. No. 5,204,250, issued Apr. 20, 1993; Shinmen et al., pp. 11-16, 1989, Appl. Microbiol. Biotechnol., vol. 31; Totani et al., pp. 1060-1062, 1987, LIPIDS, vol. 22; Shimizu et al., pp. 509-512, 1992, LIPIDS, vol. 27; Shimizu et al., pp. 342-347, 1989, JAOCS, vol. 66; Shimizu et al., pp. 1455-1459, 1988, JAOCS, vol. 65; Shimizu et al., pp. 254-258, 1991, JAOCS, vol. 68; Sajbidor et al., pp. 455-456, 1990, Biotechnology Letters, vol. 12; Bajpai et al., pp. 1255-1258, 1991, Appl. Environ. Microbiol., vol. 57; Bajpai, pp. 775-780, 1991, JAOCS, vol. 68; and Gandhi et al., pp. 1825-1830, 1991, J. Gen. Microbiol., vol. 137. The arachidonic acid productivity by the microorganisms disclosed by prior investigators, however, is less than 0.67 grams per liter per day. Such amounts are significantly less than the amounts of arachidonic acid produced by the microorganisms of the present invention. These lower productivity values are the result of employing strains: (1) with slow growth or lipid production rates leading to long fermentation times (i.e., greater than 2-3 days) (Kyle, 1992, ibid.; Shinmen et al., 1993, ibid.; Shinmen et al., 1989, ibid.; Bajpai et al., 1991, ibid.; Bajpai, ibid.; and Gandhi et al., ibid.); and/or (2) that contain low arachidonic acid contents (expressed as % fatty acids) in the final oil produced (Shinmen et al., 1993, ibid.; Shimizu et al., 1989, ibid.; and Kendrick and Ratledge, 1992, pp. 15-20, Lipids, vol. 27); and/or (3) which require long periods of stress (i.e., aging a biomass for 6-28 days) to achieve high levels of arachidonic acid in a biomass (Bajpai et al., 1991, ibid. and Shinmen et al., 1989, ibid.); and/or (4) that only exhibit high arachidonic acid content in non-commercial growth conditions (e.g., malt agar plates) (Totani and Oba, 1987, pp. 1060-1062, Lipids, vol. 22). In addition, non-Mortierella schmuckeri microorganisms that have been proposed for producing arachidonic acid, in particular Pythium insidiosum microorganisms, disclosed by prior investigators (Kyle, 1992, ibid.), have been reported to be pathogenic to humans and/or animals.
Thus, there remains a need for an economical, commercially feasible method for producing arachidonic acid. The present invention satisfies that need. There also remains a need for the an economical, commercially feasible food product for the introduction of arachidonic acid produced according to the present invention into the diet of human infants.
The present invention provides for a method for economically producing arachidonic acid. One embodiment of the present invention includes a method to produce arachidonic acid, comprising culturing microorganisms of the genus Mortierella sect. schmuckeri in a medium comprising a source of assimilable organic carbon and a source of assimilable nitrogen. In another embodiment, such strains of Mortierella sect. schmuckeri are capable of producing at least about 0.86 grams per liter per day of arachidonic acid.
Yet another embodiment of the present invention includes a food product comprising lipids recovered from a microorganism of the genus Mortierella sect. schmuckeri and a food material. In particular, such lipids can be added to infant formula and baby food to increase the arachidonic acid or long chain omega-6 fatty acid content of such foods.
The present invention provides for a novel process for the production of commercially feasible amounts of arachidonic acid using a Mortierella sect. schmuckeri microorganism. One embodiment of the present process is to produce arachidonic acid by culturing microorganisms of the genus Mortierella sect. schmuckeri in a medium comprising a source of assimilable organic carbon and a source of assimilable nitrogen. The lower fungi Phycomycetes contains at least two classes, including Oomycetes and Zygomycetes. The class Zygomycetes contains at least two orders, including Entomophthorales and Mucorales. Contained within the Mucorales order are numerous genera including Mortierella. The genus Mortierella contains nine sections, including sect. schmuckeri (Gams, 1977, pp. 381-391, Persoonia, vol. 9 and Gams, 1977, p. 216, in Abstracts Vol. A-L, Second International Mycological Congress, University of South Florida). The schmuckeri sect. of the genus Mortierella contains three species referred to as Mortierella camargensis, Mortierella clausenii and Mortierella schmuckeri. 
All of the other strains of Mortierella that have been evaluated for arachidonic acid production belong to the Mortierella sections alpina, hygrophila or spinosa. It has now been recognized that strains of Mortierella sect. schmuckeri are particularly advantageous in the production of arachidonic acid compared to these other strains of Mortierella. In particular, it has been found that strains of Mortierella sect. schmuckeri are capable of producing arachidonic acid with high productivity. Strains of Mortierella sect. schmuckeri of the present invention are preferably capable of producing at least about 0.70 grams of arachidonic acid per liter per day, more preferably at least about 0.80 grams of arachidonic acid per liter per day, and even more preferably at least about 0.86 grams of arachidonic acid per liter per day. Preferably, strains of Mortierella sect. schmuckeri of the present invention are also capable of producing a total fatty acid content of at least about 20% of dry weight, preferably at least about 30% of dry weight, and more preferably at least about 40% of dry weight. Moreover, preferred strains of Mortierella sect. schmuckeri of the present invention contain at least about 20% of total fatty acids as arachidonic acid, more preferably at least about 35% total fatty acids as arachidonic acid, and even more preferably at least about 48% total fatty acids as arachidonic acid. The arachidonic acid content of cellular biomass of strains of Mortierella sect. schmuckeri of the present invention can be at least about 5% of cellular dry weight, preferably at least about 8% of cellular dry weight, and more preferably at least about 13% of cellular dry weight.
Oil recovered, such as by extraction, from a preferred strain of Mortierella sect. schmuckeri of the present invention contains at least about 20% arachidonic acid, more preferably at least about 30% arachidonic acid, and even more preferably at least about 41% arachidonic acid. As used herein, xe2x80x9clipidxe2x80x9d xe2x80x9clipid extractxe2x80x9d, xe2x80x9coilxe2x80x9d and xe2x80x9coil extractxe2x80x9d are used interchangeably.
Morphological growth forms of fungi can have a significant effect on growth and product formation in fermenters. Fungal morphology in fermenters can range from a dispersed filamentous form to a dense pellet form. Species of Mortierella sect. schmuckeri of the present invention have an advantage over previously utilized species of Mortierella, including the ability to readily grow (early in a fermentation) in a dispersed filamentous form when grown in agitated liquid cultures such as shake flasks or fermenters. Some other species of Mortierella grown in fermentation medium typically grow in the form of pellets or spherical aggregates (i.e., having the appearance of a very tight cotton ball), sometimes exhibiting a dispersed form only after several days in a fermentation. Without being bound by theory, it is believed that the growth and productivity of cells in the pellet form is limited because cells in the center of a pellet or aggregate are not exposed to the necessary nutrients contained in the fermentation medium. Traditional methods of growing these fungal populations can include increasing the agitation of the fermenter or addition of detergents in an attempt to disperse such aggregates and improve cell growth. The present inventor has discovered that strains of Mortierella sect. schmuckeri of the present invention readily grow in the dispersed filamentous form, thereby improving growth and productivity of such cells by enabling nutrients to reach all the cells. As used herein, the term xe2x80x9cfilamentousxe2x80x9d refers to the growth of fungi as a loosely branched network of short mycelia rather than as a pellet or aggregate.
Preferred strains of Mortierella sect. schmuckeri of the present invention include strains of Mortierella sect. schmuckeri isolated from cold, arid soil, in which the microorganisms experience short periods of wetness. In particular, such areas can include soils that experience some prolonged periods of freezing or near freezing conditions. More preferred strains of Mortierella sect. schmuckeri are isolated from the Southwest region of North America, in particular, desert regions of the United States and/or Mexico. In particular, strains of Mortierella sect. schmuckeri of the species Mortierella schmuckeri are isolated from southern California and/or Mexico.
Strains of Mortierella can be isolated from soils or aquatic habitats using techniques known in the art (Stevens, 1974, in Mycology Guidebook, University of Washington Press, Seattle; and Barron, pp. 405-427, 1971, in Methods of Microbiology, Vol. 4.). More specifically, species of Mortierella sect. schmuckeri can be isolated by suspending small samples of soil in distilled water and then streaking a portion of the suspension on corn meal agar plates or agar plates containing a desired fermentation media. Additionally, species of Mortierella sect. schmuckeri can be isolated from aquatic habitats using techniques known in the art (see, for example, U.S. Pat. No. 5,130,242, by Barclay et al., issued Jul. 14, 1992; and U.S. Pat. No. 5,340,594, by Barclay et al., issued Aug. 23, 1994). On agar plates, Mortierella colonies can be partly identified by several characteristics, including for example, as white colored colonies which grow essentially within the agar rather than predominantly exhibiting aerial growth. Mortierella colonies can also be distinguished from other fungi using the general characteristics of fungal taxonomy outlined, for example, by Talbot (Principles of Fungal Taxonomy, 1971, Macmillan Press). After isolation of a pure colony, members of the genus Mortierella can also be identified by, for example, a garlic-like odor when cultured in a shake flask or in agar plate cultures containing media described in Stevens, ibid. The culture producing the best sporulation can then be used to identify the species of the culture using the Mortierella keys outlined in Gams (pp. 381-391, 1977, Persoonia, Vol. 9; and in Taxonomic problems in Mortierella, Abstracts, 2nd International Mycological Conference, University of South Florida, Tampa, published by Hamilton Newell, Inc., Amherst, Mass.).
After isolation of a pure colony of strains of Mortierella sect. schmuckeri, the biomass of the strain can be analyzed for lipid content and arachidonic acid content by gas chromatography. Preferred colonies that exhibit rapid growth and high lipid and high arachidonic acid content can then be selected. Further selection for the presence or absence of other characteristics can also be conducted. For example, in the application of extracted lipids in infant formula for the benefit of arachidonic acid content, the presence of eicosapentanoic acid (C20:5nxe2x88x923; xe2x80x9cEPAxe2x80x9d) is detrimental. Therefore, one can select for the absence of high EPA content.
One preferred species of Mortierella sect. schmuckeri of the present invention is Mortierella camargensis. Particularly preferred strains of Mortierella camargensis of the present invention have the identifying characteristic of being able to produce about 0.86 grams of arachidonic acid per liter per day. Another identifying characteristic is that between about 25% and about 33% of the total fatty acids produced by such particularly preferred Mortierella camargensis can be arachidonic acid. Thus, the resulting arachidonic acid content of a biomass of a particularly preferred Mortierella camargensis of the present invention can be between about 9.6% and about 10.8% under appropriate fermentation conditions. Yet another identifying characteristic is that the resulting oil recovered from a particularly preferred Mortierella camargensis of the present invention can have an arachidonic acid content ranging from about 20% to about 30% of the total fatty acids.
Another particularly preferred species of Mortierella sect. schmuckeri of the present invention, Mortierella schmuckeri has the identifying characteristic of being able to produce about 0.84 grams of arachidonic acid per liter per day. Another identifying characteristic is that between about 40% and about 49% of the total fatty acids produced by such particularly preferred Mortierella schmuckeri of the present invention can be arachidonic acid. Thus, the resulting arachidonic acid content of a biomass of a particularly preferred Mortierella schmuckeri of the present invention can be between about 12.5% and about 13.6% under appropriate fermentation conditions. Yet another identifying characteristic is that the resulting oil recovered from a particularly preferred Mortierella schmuckeri can have an arachidonic acid content ranging from about 33% to about 41% of the total fatty acids.
It is within the scope of the present invention that, in addition to known strains of Mortierella sect. schmuckeri, such as those on deposit with the American Type Culture Collection (e.g., ATCC), newly identified strains from nature and mutant strains derived from known or newly identified strains, can be used to produce arachidonic acid. Naturally-occurring mutants of a parental strain of Mortierella sect. schmuckeri that are capable of producing arachidonic acid can be isolated by, for example, subjecting a parental strain to at least one round of chemical or physical mutagenesis in order to increase the rate of mutagenesis, thereby increasing the probability of obtaining a microorganism producing increased amounts of arachidonic acid. It will be obvious to one skilled in the art that mutant microorganisms of the present invention also include arachidonic acid-producing microorganisms that can be obtained by genetically-engineering microorganisms to produce increased amounts of arachidonic acid. For example, it is within the purview of the present invention to transform Mortierella sect. schmuckeri microorganisms with nucleic acid molecules encoding enzymes of the arachidonic acid biosynthetic pathway obtained from fungal arachidonic acid-producing microorganisms, such as those of the genus Mortierella sect. schmuckeri. A Mortierella sect. schmuckeri nucleic acid molecule of the present invention can be obtained from its natural source either as an entire (i.e., complete) gene or a portion thereof capable of forming a stable hybrid with the entire gene. A nucleic acid molecule from a strain of Mortierella sect. schmuckeri can also be produced using recombinant DNA technology (e.g., polymerase chain reaction (PCR) amplification, cloning) or chemical synthesis. As used herein, a xe2x80x9cmutated microorganismxe2x80x9d is a mutated parental microorganism in which the nucleotide composition of such microorganism has been modified by mutation(s) that occur naturally, that are the result of exposure to a mutagen, or that are the result of genetic engineering.
Preferred mutants of strains of Mortierella sect. schmuckeri of the present invention have one or more of the identifying characteristics of a preferred Mortierella camargensis of the present invention and a preferred Mortierella schmuckeri of the present invention as described in detail above.
In accordance with the present invention, microorganisms of the genus Mortierella sect. schmuckeri capable of producing arachidonic acid, are cultured in an effective medium, herein defined as any medium capable of promoting arachidonic acid production. Preferably, the effective medium also promotes rapid fungal growth. The microorganisms of the genus Mortierella sect. schmuckeri of the present invention can be cultured in conventional fermentation modes, which include, but are not limited to, batch, fed-batch, and continuous.
The present invention provides a method to produce arachidonic acid, comprising culturing microorganisms of the genus Mortierella sect. schmuckeri in a medium comprising a source of assimilable organic carbon and a source of assimilable nitrogen.
Sources of assimilable carbon include but are not limited to sugars and their polymers, including starches, dextrin, saccharose, maltose, lactose, glucose, fructose, mannose, sorbose, arabinose, xylose, levulose, cellobiose, and molasses; fatty acids; and polyalcohols such as glycerine. Preferred carbon sources in the present invention include monosaccharides, disaccharides, and trisaccharides. The most preferred carbon source is glucose.
Sources of assimilable nitrogen useful for fermentation of a microorganism of the present invention include simple nitrogen sources, organic nitrogen sources ad complex nitrogen sources. Such nitrogen sources include ammonium salts and substances of animal, vegetable and/or microbial origin. Such organic nitrogen sources include corn steep liquor, protein hydrolysates, microbial biomass hydrolysates, soy tone, soy meal, fish meal, meat meal, meat extract, peptone, tryptone, yeast extract, yeast, whey, ammonium sulfate, urea, ammonium nitrate and amino acids.
Preferred nitrogen sources for use in an effective medium of the present invention include complex nitrogen sources. Use of a complex nitrogen source in a fermentation medium of the present invention increases arachidonic acid production by a strain of Mortierella sect. schmuckeri of the present invention by at least about 50 percent and preferably by at least about 100 percent, either as measured by percent dry weight or percent total fatty acids in an oil, compared with a strain of Mortierella sect. schmuckeri grown in the absence of a complex nitrogen source. Suitable complex nitrogen sources include, for example, corn steep liquor, protein hydrolysates, microbial biomass hydrolysates, soy tone, soy meal, fish meal, meat meal, meat extract, peptone, tryptone, yeast extract, yeast and whey. One of skill in the art can determine which complex nitrogen source best stimulates arachidonic acid production in the strain of Mortierella sect. schmuckeri employed in a fermentation process.
In a preferred embodiment of the present invention, a fermentation is conducted in which a non-carbon nutrient, for example, nitrogen or magnesium and preferably nitrogen, is limited. In this manner, cellular metabolism is directed towards lipid production, thus enhancing the overall production of arachidonic acid.
The effective medium can contain other compounds such as inorganic salts, vitamins, trace metals or growth promoters. Such compounds can be present in carbon, nitrogen, or mineral sources in the effective medium or can be added specifically to the medium. Low concentrations of magnesium are also preferred.
During the fermentation, variables including the oxygen content, pH, temperature, carbon dioxide content, and rate of carbon source addition are controlled to maximize the production of arachidonic acid without unduly limiting the length of time during which successful fermentation can be accomplished. The optimum oxygen concentration for arachidonic acid production can be determined for any particular population of Mortierella sect. schmuckeri by variation of the oxygen content of the medium. In particular, the oxygen content of the fermentation medium is maintained at an oxygen content preferably ranges from between about 20% of saturation and about 60% of saturation.
Growth of strains of Mortierella sect. schmuckeri of the present invention can be effected at any temperature conducive to satisfactory growth of the strain; for example, between about 25xc2x0 C. and about 33xc2x0 C., preferably between about 27xc2x0 C. and about 32xc2x0 C., and more preferably at about 30xc2x0 C. The culture medium typically becomes more alkaline during the fermentation if pH is not controlled by acid addition or buffers. The strains of Mortierella sect. schmuckeri of the present invention will grow over a pH range from between about 4.0 to about 10.0 with a starting pH of about 5.5 being more preferred.
Another aspect of the present invention includes a food product comprising a food material combined with microorganisms of the genus Mortierella sect. schmuckeri. Strains of Mortierella sect. schmuckeri of the present invention are added to a food material to create a food product having enhanced concentrations of arachidonic acid. As used herein, the term xe2x80x9cfood materialxe2x80x9d refers to any food type fed to humans or non-human animals. Also within the scope of the present invention is a method to make a food product comprising adding microorganisms of the genus Mortierella sect. schmuckeri to a food material.
Mortierella sect. schmuckeri of the present invention are recovered for use as a food supplement simply by separating the cells from fermentation medium. A variety of procedures can be employed in the recovery of microbial cells from the culture medium. In a preferred recovery process, the cells produced in the fermentation process are recovered from the culture medium by separation using conventional means, such as centrifugation or filtration. The cells can then be washed, frozen, lyophilized, and/or dried (e.g., spray drying, tunnel drying, vacuum drying, or a similar process). The arachidonic acid rich oil can be extracted immediately from the cells or the resulting cells can then be stored under a non-oxidizing atmosphere of a gas such as N2 or CO2 (to eliminate the presence of O2) prior to incorporation into a food material. Alternatively, recovered cells can be used directly (without drying) as a feed supplement. To extend its shelf life, the wet biomass of a strain of Mortierella sect. schmuckeri can be acidified (approximate pH=3.5-4.5) and/or pasteurized or flash heated to inactivate enzymes and then canned, bottled or packaged under a vacuum.
A suitable food material useful for the formation of a food product of the present invention includes animal food. The term xe2x80x9canimalxe2x80x9d means any organism belonging to the kingdom Animalia and includes, without limitation, primates (e.g., humans and monkeys), livestock and domestic pets. The term xe2x80x9cfood productxe2x80x9d includes any product to be fed to such animals. Preferred food materials to be consumed by humans includes infant formula and baby food. Preferred food materials to be consumed by domestic pets includes dog foods. By adding Mortierella sect. schmuckeri biomass or extracted oil to provide a source of arachidonic acid, preferred food products of the present invention comprise a total fatty acid content in which up to about 20% by weight of total fatty acids is arachidonic acid, more preferred food products of the present invention comprise a total fatty acid content in which up to about 10% by weight of total fatty acids is arachidonic acid, and even more preferred food products of the present invention comprise a total fatty acid content in which between about 0.1% and about 1.0% by weight of total fatty acids is arachidonic acid.
A further embodiment includes a food product comprising lipids recovered from a microorganism of the genus Mortierella sect. schmuckeri and a food material. Recovered lipids can include either all of the lipids recovered from the microorganisms or a portion thereof (i.e., isolated arachidonic acid or total fatty acids containing arachidonic acid). In the former instance, the lipid composition includes arachidonic acid in about the same relative amount as it exists in the organism. Alternatively, the recovered lipids can be further processed to concentrate the arachidonic acid to achieve a composition having a greater concentration of arachidonic acid than occurs naturally in the organism. Also within the scope of the present invention is a method to make a food product comprising adding lipids recovered from a microorganism of the genus Mortierella sect. schmuckeri to a food material.
Recovery of lipids from strains of Mortierella sect. schmuckeri can be accomplished by any suitable method, including numerous methods known in the art. For example, recovery can include the following method. Harvested cells (fresh or dried) can be ruptured using techniques known to those in the art. Lipids can then be extracted from the cells by any suitable means, such as by supercritical fluid extraction, or by extraction with solvents such as chloroform, hexane, methylene chloride, methanol, isopropol, ethyl acetate, and the like, and the extract evaporated under reduced pressure to produce a sample of concentrated lipid material. Arachidonic acid can be further separated from other lipids by chilling a fatty acid composition such that the saturated fatty acids in the composition precipitate out while the arachidonic acid remains in solution. The solution can then be recovered.
The Mortierella sect. schmuckeri microorganisms can also be broken or lysed and the lipids recovered into edible oil using standard methods known in the art. The recovered oils can be refined by well-known processes routinely employed to refine vegetable oils (e.g., chemical or physical refining). These refining processes remove impurities from recovered oils before they are used or sold as edible oils. The refining process consists of a series of processes to degum, bleach, filter, deodorize and polish the recovered oils. After refining, the oils can be used directly as a feed or food additive to produce arachidonic acid enriched products. Alternatively, the oil can be further processed and purified as outlined below and then used in the applications as described herein.
Lipids recovered from the biomass of a strain of Mortierella sect. schmuckeri of the present invention can be combined with any animal food material, particularly food materials for humans, to create a food product having enhanced concentrations of arachidonic acid. The amount of fatty acids naturally in food products varies from one food product to another. A food product of the present invention can have a normal amount of arachidonic acid or a modified amount of arachidonic acid. In the former instance, a portion of the naturally occurring lipids are substituted by lipids of the present invention. In the latter instance, naturally occurring lipids are supplemented by lipids of the present invention.
Preferably, lipids recovered from strain of Mortierella sect. schmuckeri are added to foods for infants, such as infant formula and baby food. According to the present invention, an infant refers to infants in utero and children less than about two years old, including, in particular, premature infants. Arachidonic acid is a particularly important component of infant formula and baby food because of the rapid growth of infants (i.e., doubling or tripling in weight during the first year of life). An effective amount of arachidonic acid to supplement infant formula is an amount that approximates the concentration of arachidonic acid in human breast milk. Preferred amounts of arachidonic acid to add to infant formula or baby food range from between about 0.1 to about 1.0% of total fatty acids, more preferably from between about 0.1 to about 0.6% of total fatty acids, and even more preferably about 0.4% of total fatty acids.
Arachidonic acid produced by the method of the present invention is suitable for use as therapeutic and experimental agents. An embodiment of the present invention comprises the production of arachidonic acid for treatment of arachidonic acid-deficient infants. The arachidonic acid can be included in a parenteral formulation that can be administered to an infant through parenteral routes to fortify the infant""s supply of arachidonic acid. Preferred parenteral routes include, but are not limited to, subcutaneous, intradermal, intravenous, intramuscular and intraperitoneal routes. A parenteral formulation can include arachidonic acid of the present invention and a carrier suitable for parenteral delivery. As used herein, a xe2x80x9ccarrierxe2x80x9d refers to any substance suitable as a vehicle for delivering a molecule or composition to a suitable in vivo site of action. Examples of such carriers include, but are not limited to water, phosphate buffered saline, Ringer""s solution, dextrose solution, serum-containing solutions, Hank""s solution and other aqueous physiologically balanced solutions. Acceptable protocols to administer arachidonic acid in an effective manner include individual dose size, number of doses, frequency of dose administration, and mode of administration. Determination of such protocols can be accomplished by those skilled in the art depending upon a variety of variables, including the weight of the infant and the extent of arachidonic acid deficiency. Another embodiment of the present invention comprises the production of arachidonic acid for treatment of adults, in particular pregnant mothers. Acceptable protocols for administration of arachidonic acid to adults includes parenteral feeding techniques or encapsulating oil recovered from a microorganism of the present invention in a capsule, such as gelatin (i.e., digestible) capsule, for oral administration and/or in a liquid diet formulation. A liquid diet formulation can comprise a liquid composition containing nutrients suitable for supplementing a diet or nutrients sufficient as a complete diet.
Another embodiment of the present invention comprises the production of arachidonic acid for use as an experimental reagent to identify regulators of metabolic pathways for which arachidonic acid is a precursor. For example, arachidonic acid is a precursor for leukotrienes. Leukotrienes are believed to be involved in the occurrence of certain diseases involving inflammation and allergy. As such, inhibitors of leukotriene production may be valuable therapeutic agents. Arachidonic acid recovered using the method of the present invention can be used to test putative inhibitory agents in vitro by incubating the putative inhibitor with arachidonic acid under suitable conditions well-known to those of skill in the art, and measuring leukotriene production.
The following examples and test results are provided for the purposes of illustration and are not intended to limit the scope of the invention.